Method and apparatus for concentrating sulphuric acid



s sheets-sheet i ATTORNEYS Filed Sept Jan. 27, 1931.,

Jan. 27, 1931. w. c. MAST METHOD AND APPARATUS FOR CONCENTRATIVNGSULPHURIC ACID Filed sept. 22, 192? 3 sheetssheet 2 .H'' Fg 47 INVENTOR.l//Y//a'f/v /Vds BY Mq M/ W f A TTORNEYS Jan. 27, 1931. I C, MAST1,790,507

METHOD AND APPARATUS FOR CONCENTRATING SULPHURIC ACID Filed Sept. 22,1927 3 Sheets-Sheet 5 BY M, f? M/ ATTORNEYS v Patented Jan. 27, 1931UNITED 'STATES' PATENT OFFICE WILLIAM C. MAST, OF LONG BEACH,CALIFORNIA, ASSIGNOR, BY MESNE ASSIGNMENTS, TO CHEMICAL CONSTRUCTIONCORPORATION, VA. CORPORATION OF DELAWARE METHOD AND APPARATUS FOB,CONCENTRATING SULPHURIC ACID Application med September 22, 1927. SerialNo. 2121,15?. R U

This invention relates to the concentrating of sulphuric acid and isparticularly intended for concentration of sludge acid, that is to sathe acid recovered from thesludge resu ting from the usual acidtreatment of hydrocarbon or petroleum oils. While certain of theadvantages of the process are more pronounced in the case of sludge acidconcentration, the invention is, however, applicable to sulphuric acidconcentration in general.

The main object of the invention is to provide a more economical andeffective process and apparatus for concentrating sulphuric acid thanhave heretofore been in uz-ze.

Further and more particular objects of the invention are to provide forcomplete and efficient utilization of the available heat in the hotgases used for effecting the concentration, to permit the use of anapparatus having a lower first cost as well as a minimum cost ofmaintenance due to the practically indestructible construction thereof,to provide for absorption of acid vapors by bubbling the gases passingfrom a more concentrated portion o f acid through a less concentratedportion of acid, thereby eliminating expensive absorption towers, tosubstantially eliminate all leakage of fumes from the concentrator andto permit a high degree of accessibility to all parts of the apparatus.

The method by which these'operations are accomplished consists brieflyin maintaining a plurality of bodies of acid defining a plurality ofstages, continuously passing acid through' said bodies or stages insuc-cession, and causing a stream of hot gases to be successivelydelivered,preferably under pressure,

beneath the surface of the respective bodies of acid so as to bubbleyupwardly therethrough, the gases after passing through one of saidbodies of acid being delivered to and bubblcd through another body ofacid and so on. The direction of flow of hot gases through thesuccessive bodies of acid is, in general, preferably counter-current tothe direction of How of acid, although some dcparturc may occasionallybe advantageously made from this procedure, as hereinafter described. Inthe case of straight counter-current flow the hot gases pass firstthrough the body of most concentrated acid, then to the preceding bodyof acid containing slightly weaker acid and so on until they are finallypassed through the most dilute acid.

v This process may be carried out in a single horizontal cylindricalsteel tank or drum, lined with lead and acid-resisting brick, andpartitioned into a number of compartments through which the acid isconducted successively, the partitions being provided with slantingducts leading from above the surface of the acid in one compartment tobelow the surface of the acid in the next succeeding compartment in thedirection of gas flow. The apparatus may, however, comprise a. pluralityof smaller separate tanks connected for successive flow of acidtherethrough and provided with suitable ues for conducting the gases`from above the acid in one tank to beneath the surface of the acid inanother, or it may consist of a combination of these two schemes, or anyother suitable arrangement of Y chambers 'for accom lishin the sameresult. The use of cylindrlcal tan rs lined with lead and acid-proofbrick is, however, of particular advantage, since the cylindricalconstruc.

tion maintains the bricks tightly in position at all times and preventschecks and leakage of acid and fumes which is inherent in other types ofconcentrating plants. 1 Furthermore, these tanks will last practicallyindefinitely and minimize the maintenance cost.

It may be seen that as the hot gases pass -from each stage or body ofacid to the next they contain acid vapors carried off from the bodythrough which they have ]ust passed. By delivering,r these. gasesbeneath the surface of a body of weaker lacid, which is also cooler`acid are substantially all absorbed, the exit gases are substantiallyfree from acid, containing onl such partlcles as are carried overmechanical in sus nsion and which can be removed y suitab e means suchas a small scrubbing tower or box.

An important advantage of this method consists in the releasing of thehot gases bcneath the surface of the acid so as to rovide a largesurface for evaporation o water therefrom and to also agitate the acid.The increased rate of evaporation obtained in this manner permitsconcentration to be effected at the same rate as though the boilingpoint were actually lowered more than 100 F. below its true boilingpoint at the prevailing pressure; and the lower temperatures which maytherefore be used minimize decomposition of acid and facilitateabsorption of acid fumes in the successively weaker andcooler` acids andfinally help to condense the last `traces of acid mist in the exitgases.I The temperature of the exit gases may readily be reduced by thismethod to not more than 230 F., and it may, therefore be seen that ahigh proportion of available heat in the gases is utilized.

The hot gases employed in this process may consist of hot combustlongases, with or without a certain proportion of excess air, and such hotgases may be produced in any suitable type of furnace or combustionapparatus.

Whi e, as above stated, the direction of gas flow is referably ingeneral counter-currentto the ow of acid, it may be found desirable insome cases, especially when impurities are present (as in concentrationof sludge acid), to pass the hot gases first through a compartment ofless concentrated acid and then pass the partly cooled gases through thebody of strongest acid, so as to prevent decomposition of the strongacid by the hot gases in the presence of such impurities.

The accom anying drawings illustrate apparatus whic is suitable forcarrying out the above described operations and which also forms a part'of the resent invention. Referring to these drawm Fig. 1 is a partlysectional form of such ap aratus.

Fig. 2 is a section on line 2--2 in Fig. 1.

Fig. 3 is a transverse section on line 3-3 in Fig. 2.

Fig. 4 is a section on line 4-4 in Fig. l.

5 is a section on line 5-5 in Fig. 1.

Fig. 6 is a longitudinal section of a modified form of apparatus.

Fig. 7 is a longitudinal section of another modification.

Fig. 8 is a section on line 8--8 in Fig. 7.

The apparatus shown in Figs. 1, 2 and 3 comprises twoA horizontalcylindrical steel tanks 1, each of which is provided with a lead lining2 and also with a lining 3 vof acidresisting brick within said leadlining, said plan view of one acid-resisting brick being laid up inacidresisting cement to revent corrosive action of the hot acid on t emetal. Each of these tanks is divided by a partition 5 into two chambersor bompartments said compa-rtments bein numbered 6a, 6b, 6c, and 6d inthe order 1n which the acid passes therethrou h in the case of straightcounter-current ow. The acid may be delivered to chamber 6a by means ofpipe`8, thence by means of pipe 9a, over-flow device 10a, and pipe 11ato chamber 6b, thence through 9b, 10b, and 11b to chamber 6c, thenthrough 9c, 10c and 110 to chamber 6d, while the concentrated acid maybe delivered through pipe 9d, over-flow device 10d, and pipe 11d to anysuitable point for further disposition. The several pipes 9a, 9b, etc.,preferably lead from the lowermost portion of the respective chambers soas to permit draining or flushing of said chambers through the over-flowdevices as hereinafter described, while the ipes 11a, 11b, etc.,.mayopen into said cham ers at an suitable height below the normal level oft e acid therein.

Any suitable ty of furnace or combustion chamber 15 may e provided,having burner means 16 for the combustion of fuel and being connected bylines 17 to the gas delivering pipes leading into the acid chamber 6d.The hot gases are referably forced through the apparatus un er pressureby supplying air un er pressure through flue 16 to furnace 15.

Connection from flue 17 to the pipes 2O may be provided by means ofshort connecting pipes 18, said pipes 18 and 2O being connected bsuitable expansion joint means 19 provide with packing 21 which serve topermit expansion and contraction of said pipes without causing unduestrain thereon. The pipes 20 may extend through openings 22 in the bricklining 3, suitable packing 24 being provided around said pipes. The leadlining 2 is preferably doubled back over the edges of the steel shell 1around said opening as indicated at 25 and a sleeve 26 may be provided,being secured to said lining and steel shell and extendinvupwardlyaround pipe 20 and being secured at its upper end to thc members of theexpansion joint 19 as at'27.

The pipes 20 extend to a suitable depth below the normal acid level inchamber 6d, and are open at their lower ends as shown at 30. In order todeliver the ases from chamber 6d to 6c, the artition 5 t erebetween maybe provided wit a plurality of slanting ducts 32 which extend from abovethe acid level in the first of said chambers to below the acid level inthe second chamber. Batlle -33 may be provlded for minimizing mechanicalentrainment of liquid particles through the ducts 32. From chamber 6cthe gases may be led by means of flue 35 'and delivery pipes 36 tobeneath the surface of the acid in chamber 6b,

lll@

level iii 6b to below the acid level in 6a, and

with a baille plate 38 similar to baffle plate 33. A gas exit flue 40leads from the top of chamber 6a, for conducting the hot gases to astack or to a suitable apparatus for recovery of arid mist or vaporstherefrom ,suchV Yas a scrubbing tower or the like.

Each of the overflow devices-may be similar p in construction totheyover-flow device 10d which is illustrated more particularly in Fig.5. Such device comprises a tubular casing having a base 46 and coverplate 47. An inlet passage 48 extends through the'base 46 andcommunicates with a central recess 49 there-4 in. A drain passage 50extends downwardly from said recess 49 through the bottom of base 46,while an outlet passage' 51 leads from the interior of casing 45 throughthe wall thereof.- The passage means 48, 50 and 51 may be flanged attheir outer ends as indicated, for connection of pipes thereto in wellknown manner. An overflow pipe 53 may be provided within the casing 45and having :i base portion 54 engaging in recess 49. Said base portionand recess are preferably tapered as shown and ground so as to provide asnug fit when the overflow pipe is lowered into said recess. Saidoverflow pipe is provided with a port 55 communicating with theinletpassage 48. The height of overflow pipe 53 may be adjusted byaddition ot' .pipe sections or rings 56 of varying heights at the upperend thereof, so as to regulate the height of the acid level in the tankwhich is connected to inlet passage 48. In practice v the respectiveoverflow pipes are preferably made of such height as to provide for aslight decrease in acid level in the successive tanks and thus maintaina steady flow of acid through the tanks. It will be apparent that withthe overflow pipe in the position shown in Fig. 5, the acid, coming inthis case from tank (3a', will be caused to flow upwardly within saidpipe and over the upper edge thereof into the interior of casing 45 andthen out through passage 51. However, by

.simply removing the cover plate 47 and rais,

ing overflow pipe 53 out of tlie recess 49, communication is establishedfrom inlet passage `lf8 through said recess to drain passage-50 so as topermit draining or flushing of the acid compartment to which thevdeviceis connectedf The overflow pipe, therefore, also constitutes aremovable plug for controlling flow of liquid through the drain opening.

'llie mannerfof carrying out the process in the above describedapparatus will be apparent from the above description. Hot combustiongases are produced under pressure in furnace 15 and suchgases are firstdelivered at suitable pressure through ipesv 20 beneath the surface ofthe liquid in c amber 6d. 'In bubbling up through this body of acid thegases agitate and heat the same and car off water'vapor therefrom,together with some acid fumes. then pass through ducts 32 to chamber 6c,wherein this process is repeated and so on through the chambers 6b and6a. A continual flow of acid is maintained through the chambers in thereverse direction, the rate of These gases such flow being controlled bythe rate at which dilute acid is supplied to the apparatus through pipe8, and the proportion of concentration effected in each chamber beingregulated by controlling the de th of acid therein by means of the-Yover ow devices above described.

As stated above, it may be advantageous `in some cases to depart fromstraight countercurrent flow of gases and acid, to the extent of passingthe hot gases first through a less concentrated body of acid in order topartially cool sucli gases before delivering the same to the mostconcentrated acid. T i accomplished in the apparatus above described bsubstituting pipes 12b, 12o, and 12d, (as s iown in dotted lines in Fig.l) for the'pipes 11b, 11e, and 11d, so that the acid is caused to passfrom chamber 6b to chamber 6d, and then to chamber 6c. The gases thuspass first through a. less concentrated body of acid in chamber 6d andthen through pthel most concentrated acid in 60.

In the apparatus shown in Fig. 6 the chambers 6a, 6b, 6c and 6d are allprovided Within asingle cylindrical tank 60 provided as bes may be forewith lead lining 61 and acid proof brick i lining 62. Said chambers areseparated as before by means of partitions 63 provided with inclinedducts 64 extending from above the shown in Figs. 7 and 8 in which thesuccessive bodies of acid are contained in separate cylindrical tanks 68lined as before with lead 69 and acid proof brick 70, and placed side byside. While ll have shown only three chambers 6a, 6?), and 6c in thiscase it will be understood that any suitable number of chambers may beused in any of the forms of theinvention. The hot gases are delivered,as before,

beneath the surface of the acid in .the cham-- ber 60, as by means of aplurality of pipes 72,

while pi es 73 extend'from the upper portion of cham er 6c to the lowerportion of chamber 6b, and pipes 74 from the 'upper portion of chamber65, to the lower poi-tion of chamber 6a. Pipes 75 conduct the gases awayfrom the upper part of chamber 6a. Batlle plates 76 may be provided forpreventing entrainbodies of aci ment of liquid acid from one chamber tothe next. Pi es 8, 9a, 11a, 9b, 11b, 9c and 110 and ove ow devices 10a,10b, and 10c are rovided, as before, for effecting and controlb'ng flowof acid through the successive chamers.

Certain features of this invention may be advantageously applied inconjunction with the well known tower process of sulphuric acidconcentration. For example, one or more of the acid chambers of any ofthe forms above described may be placed ahead of the concentrating towerin an apparatus such as shown, for example, in the patent toHechenbleikner 1,456,874, and the acid may be passed first through thetower and then through said chamber or chambers, while the-hot gasespass first through the chambers in the same manner as above described,and then upwardly through the tower in contact with the acid.

An advantage of this invention is the absence of exposure of a smallstream of acid to gases at high temperature or to highly heated checkerwork structures, as in the ordinary tower process. The tower usuallyemployed in such process consists of a checker work of acid proof brickand a relatively small stream of acid is allowedto How downwardlythrough such checker work while thel hot gases pass upwardlytherethrough. The acid flow is frequently irregular in different partsof the tower, and portions of the checker work often become over-heatedso that when acid is again brought into contact therewith, decompositionresults, particularly in the presence of hydrocarbons such as arepresent in sludge acids. This decomposition is not only substantiallyeliminated by the practice of this invention, without the use of atower, but is also minimized by the combination of this n1- vention withthe tower process as above described, since in that case the hot gasesare first cooled by one or more passages through the acid beforebringing the same into contact with the acid in the tower.

I claim:

l. The method of concentrating sulpburic acid which consists inmaintaining a plurality of separate bodies of acid, continuously passingacid through said bodies in succession and causin a stream of hot easesto be successively de ivered to and reeased beneath the surface oftheres ective bodies of acid so as to pass upwardly t erethrough, thegases after assing through one of said d) bein delivered to and assedthrough another of; said bodies of aci 2. The method as set forth inclaim 1, in which the order of passing the as through the bodies of acidis reverse to t 1e direction of passage of acid therethrough.

chambers, and also passing a stream of hot gases under positive pressuresuccessively throu h said chambers, said gases being conducted fromabove the surface of the acid in one of said plurality of chambers tobeneath the surface of the acid in another of said plurality ofchambers, whereby the acid is eated to successively higher temperaturesand concentrated to successively higher concentrations in the successivechambers in the direction of acid iiow and the gases are cooled tosuccessively lower temperatures in the successive chambers in thedirection of 4gas flow therethrough.

4. The method as set forth in claim 3, in which the direction of gas Howto the successive chambers is reverse to the direction of acid flowtherethrough.

5. An apparatus for concentrating sulphuric acid comprising meansdefining a plurality of chambers, means for passing acid 'through saidchambers in series, and means for causing hot gases to pass underpositive pressure successively through said chambers and for causing thegases to pass from above the acid level in one of said chambers tobelowthe acid level in another of said chambers in the direction of gasflow.

(i. An a paratus for concentrating sulphuric aci( com rising a pluralityof' cylin drical metal tanks lined with acid resistant material, acidconducting pipes connecting said tanks in series and provided with meansfor maintaining a definite acid level in each tank, and gas conductingpipes connecting said tanks in series and extending from above the acidlevel in one tank to below the acid level in another tank.

7. In an apparatus for concentrating sulphuric acid, means defining twochambers. means for delivering hot gases to the lower portion to thefirst chamber, means for conducting hot gases from the upper portion ofthe first chamber to the lower portion of the second chamber, meanspermitting outfiow of gases from the upper portion of said secondchamber, and means for delivering acid to said second chamber, forpassing acid from said second chamber to said first chamber, and forconducting acid away from said first chamber.

8. The method of concentrating sulphuric acid which consists inmaintaining the acid in separate bodies defining a plurality of separatestages, in flowing the acid through said stages serially forprogressively increasing concentration,fand in flowing cated gasesserially through and beneath the surface of the acid bodies in saidplurality of stages for effecting the progressive concentration of saidacid, the gases being delivered to each of the acid bodies below thesurface thereof and said` gases after fiowing through the acid body inone of said stages being delivered to the acid body in another of saidstages.

A 9. The method of concentrating sulphuric llO acid which consists inmaintaining the acid in separate bodies defining a plurality of separatestages, and in flowing heated gases serially through andbeneath thesurfaces'of the acid bodies in said plurality of stages, the

gases being delivered to each' of the acid bodies below the surfacethereof so as to pass upwardly therethrough, and said gases after owingthrough the acid body in one of said .stages being deliveredl to theacid body in another of said stages.

In testimony whereof I have hereunto subscribed myname this 13th day ofSeptember,

e WILLIAM C. MAST.

